Instantaneous/Tankless Water Heaters

Instantaneous or tank-less water heaters are very common in Europe and Asia. Unlike storage heaters, instantaneous water heaters heat water only upon activation by switch or flow.

Advantages:

They do not suffer from standby heat loss
They have much smaller space requirements

Disadvantages:

For safety reasons, they have high minimum flow rate required to activate
Water temperature is dependent on volume of water; for a given heating setting, higher/stronger water means lower temperature